1. Technical Field
Embodiments of the subject matter disclosed herein generally relate to a canted helix flowmeter including a spinner arm configured to be deployed at a predetermined angle with a fluid flow direction and having helical blades.
2. Discussion of the Background
Since oil and gas remain a source of energy that cannot be replaced at a significant enough proportion in the world economy, the interest in developing new production fields has continued to increase, in spite of the harsher conditions in terms of accessibility and safety of exploitation. Thus, oil wells are developed undersea and flow measurements inside the well are often desirable.
A flow measurement quantifies an amount of a moving fluid. In gas and oil wells, local or systematic variations of the fluid flow render the flow measurement more challenging. For example, when a multiphase fluid flow is measured in an inclined pipe (even for small inclinations) a phase segregation may occur, when lighter phases migrate to a high side (in a plane perpendicular to the flow direction) of the well, while heavier phases migrate to a low side of the well. Locally or related to different phases mixed in the fluid, the fluid may have different velocities or even flow in different directions.
A conventional tool used to measure a fluid flow in a borehole is a spinner tool array 1 illustrated in FIG. 1. The spinner tool array 1 includes six flow sensors 10 attached to bowspring arms 20 that emerge from a tool body 30. The bowspring arms 20 are retracted inside the tool body 30 during transportation through a restriction to a measurement location inside the borehole. The sensors 10 are deployed to be parallel to a fluid flow direction 40, at different locations away from the tool body's central position, up to edges of the borehole.
FIG. 2 illustrates a flow sensor 10 of the spinner tool array 1. The flow sensor 10 includes an impeller 60 of about 9 mm diameter and about 25 mm length. The impeller 60 spins like a mini-turbine due to the fluid flow. In order to be able to spin, the impeller 60 is mounted on a holding structure 70 via bearings 80 and 80′. The rotation speed of the impeller 60 depends on the speed of the fluid. The fluid flow is calculated based on the rotation speed of the impeller 60. The rotation speed may be measured, for example, by measuring an electromagnetic signal generated by small magnets that are embedded in the impeller 60. The generated signal may be picked-up by an appropriate device located inside the holding structure 70.
A problem observed in using the spinner tool array 1 inside an oil and gas well is the clogging of the bearings 80 and 80′ with dirt or other particles. When the bearings 80 and 80′ are clogged, a friction in the bearings increases, and the rotation speed of the impeller 60 decreases (sometimes down to zero). Thus, the spinner tool array 1 does not provide a reliable flow measurement in an oil and gas well, due to the vulnerability of the flow sensors to the environment.
Additionally, one of the bearings (e.g., 80 in FIG. 2) and a part of the holding structure 70 are disposed in the path of the fluid flow, before the impeller 60 (the other bearing is located after the impeller 60), thus partially blocking the fluid flow moving towards the impeller 60. This arrangement affects the accuracy of the flow measurement using the spinner tool array 1.
Accordingly, it would be desirable to provide systems and methods that avoid the afore-described problems and drawbacks.